1. Field of the Invention
The present invention relates to an informing system and method, and more particularly to an informing system and method utilizing electromagnetic and acoustic signals emitted from an approaching emergency vehicle or similar for providing a warning of the presence of and determining the time until metting with a stationary or moving receiver.
2. Description of the Prior Art
Acoustical sirens for signaling the presence of emergency vehicles were adopted over fifty years ago when the prevailing construction of motor vehicles afforded relatively easy access to such signals. Soundproofing provided by the current design of motor vehicles and the background noise of internal radios, heaters, air conditioners and other sound producing devices have greatly reduced the effectiveness of acoustical sirens for this use. In addition, hearing impaired drivers are put at risk whenever they are unable to see the flashing lights or similar from an emergency vehicle due to intervening objects. Various methods and systems have been proposed to inform the driver of a motor vehicle of the proximity of an emergency vehicle.
The system disclosed by U.S. Pat. Nos. 3,873,963 and 4,380,004 use acoustical signals emitted from an emergency vehicle to cause an alarm to be triggered inside a proximate motor vehicle, but do not provide the driver with information regarding the distance between vehicles or how long before the vehicles meet. The system disclosed by U.S. Pat. No. 4,238,778 uses electromagnetic signals emitted from an emergency vehicle to cause an alarm to be triggered inside a proximate motor vehicle, and gives the driver some indication of the relative distance between the vehicles by the use of a variable frequency audio alarm signal, but does not provide the driver with information regarding how long before the vehicles meet. The system disclosed by U.S. Pat. Nos. 3,566,348 and 3,731,273 use both acoustical and electromagnetic signals to determine the relative distance and direction of two objects, but do not provide information regarding how long before the objects, if moving, would meet. The system disclosed by U.S. Pat. No. 3,784,970 uses both electromagnetic and acoustical signals emitted from an emergency vehicle to cause an alarm to be activated inside a motor vehicle that is closer than a predetermined range, but does not provide the driver with any other information regarding the distance between the vehicles or how long before the vehicles meet.
Despite the availability of such systems, there exists a need in the art for an improved approaching vehicle informing system and method that informs the driver of a motor vehicle when a proximate emergency vehicle is relatively approaching, and, in addition, gives information to the driver as to the time until the emergency vehicle and the driver's vehicle meet, thereby permitting the driver to make an informed judgment as to the most appropriate action to take in view of the surrounding circumstances.